Water reactive polyurethane grout materials have been introduced into grouting industry for decades. It is well known that polyurethane grout materials can react with the in-situ water to form a foam or gel. Numerous successes are reported using polyurethane grouts for water leakage and seepage control in mining and geotechnical engineering projects due to high reactivity of isocyanates and high dilution ratio with water. However, a major challenge underlying polyurethane grout materials to be used under high water pressure environment with performance needed including reactivity, mechanical properties, adhesion and durability has not been addressed. This is especially important for applications, such as core drilling exploration for mining and shale gas, foundation excavation and quick seepage control for underground tunnel joints. Therefore, it would be desirable to develop a polyurethane grout composition which could meet the grouting needs of the application under high water pressure environment.
In the prior art, WO2008134359 discloses elastomer compositions of blocked isocyanate prepolymer used in downhole applications. WO2008134371 describes using silane terminated polymers as grout materials and releases a method of treating an earth formation comprising introducing at least one curable liquid composition intended to form an elastomer in a liquid phase into the earthen formation; introducing at least one curing agent into the earthen formation; and contacting the at least one curable liquid composition and the at least one curing agent to form a non-aqueous gel. Although WO2008134359 and WO2008134371 describe the grout application for core drilling exploration, these patents clearly are not focused on polyurethane prepolymer design and composition.
In addition, WO2010067126 describes compositions comprising a potassium silicate and/or sodium silicate powder having a water content of substantially 0% w/w and an isocyanate, processes for preparing and hardening these compositions, a rock bolt filled with the composition and a rock bolting capsule formed by a water impermeable membrane and containing the composition. CA2713384 emphasizes on using silane materials for grout application. US2005148726 describes a specialized application of polyurethane materials with improvement on stain resistance by incorporation of fluoro-materials.
Other two related patents include CN102093536, which relates to a polyurethane prepolymer, a polyurethane grouting material and a preparation method thereof, and CN102079862 which discloses a single-component oil-soluble polyurethane grouting material, and raw materials and a preparation method thereof. However, it is found that neither these two hydrophobic grouting materials described in CN102093536 and CN102079862 can cure under water pressure above 1 MPa.
CN102093537 discloses a preparation method of a waterborne polyurethane grouting material. Isocyanate, retarding agent and hydrophilic polyether polyol are mixed to react and obtain the finished product.
CN102079863 discloses a single-component hydrophilic polyurethane grouting material, as well as raw materials and a preparation method thereof.
The grouting material of CN102093537 and CN102079863 are both hydrophilic PU grout. According to the testing results of the present invention, such grouting material forms a gel with poor mechanical properties and poor adhesion to the substrate under high water pressure.
After a thorough prior art study, it is found that none of the documents cited above teaches or suggests the present invention.